From 5730fd49fa0379141ca78c59f5514c206ed8e53f Mon Sep 17 00:00:00 2001
From: Alex Macleod <alex@macleod.io>
Date: Fri, 20 May 2022 12:39:15 +0000
Subject: [PATCH] Lint indirect usages in `disallowed_methods`

---
 clippy_lints/src/disallowed_methods.rs        | 14 ++++++++++---
 .../conf_disallowed_methods.rs                |  6 ++++++
 .../conf_disallowed_methods.stderr            | 20 ++++++++++++++++++-
 3 files changed, 36 insertions(+), 4 deletions(-)

diff --git a/clippy_lints/src/disallowed_methods.rs b/clippy_lints/src/disallowed_methods.rs
index 4c12202c8..53973ab79 100644
--- a/clippy_lints/src/disallowed_methods.rs
+++ b/clippy_lints/src/disallowed_methods.rs
@@ -1,7 +1,7 @@
 use clippy_utils::diagnostics::span_lint_and_then;
-use clippy_utils::fn_def_id;
+use clippy_utils::{fn_def_id, get_parent_expr, path_def_id};
 
-use rustc_hir::{def::Res, def_id::DefIdMap, Expr};
+use rustc_hir::{def::Res, def_id::DefIdMap, Expr, ExprKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_tool_lint, impl_lint_pass};
 
@@ -84,7 +84,15 @@ impl<'tcx> LateLintPass<'tcx> for DisallowedMethods {
     }
 
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
-        let def_id = match fn_def_id(cx, expr) {
+        let uncalled_path = if let Some(parent) = get_parent_expr(cx, expr)
+            && let ExprKind::Call(receiver, _) = parent.kind
+            && receiver.hir_id == expr.hir_id
+        {
+            None
+        } else {
+            path_def_id(cx, expr)
+        };
+        let def_id = match uncalled_path.or_else(|| fn_def_id(cx, expr)) {
             Some(def_id) => def_id,
             None => return,
         };
diff --git a/tests/ui-toml/toml_disallowed_methods/conf_disallowed_methods.rs b/tests/ui-toml/toml_disallowed_methods/conf_disallowed_methods.rs
index 338b3b5b2..3397fa1ec 100644
--- a/tests/ui-toml/toml_disallowed_methods/conf_disallowed_methods.rs
+++ b/tests/ui-toml/toml_disallowed_methods/conf_disallowed_methods.rs
@@ -14,4 +14,10 @@ fn main() {
 
     let _ = 2.0f32.clamp(3.0f32, 4.0f32);
     let _ = 2.0f64.clamp(3.0f64, 4.0f64);
+
+    let indirect: fn(&str) -> Result<Regex, regex::Error> = Regex::new;
+    let re = indirect(".").unwrap();
+
+    let in_call = Box::new(f32::clamp);
+    let in_method_call = ["^", "$"].into_iter().map(Regex::new);
 }
diff --git a/tests/ui-toml/toml_disallowed_methods/conf_disallowed_methods.stderr b/tests/ui-toml/toml_disallowed_methods/conf_disallowed_methods.stderr
index 5533676ae..5cbb56754 100644
--- a/tests/ui-toml/toml_disallowed_methods/conf_disallowed_methods.stderr
+++ b/tests/ui-toml/toml_disallowed_methods/conf_disallowed_methods.stderr
@@ -32,5 +32,23 @@ error: use of a disallowed method `f32::clamp`
 LL |     let _ = 2.0f32.clamp(3.0f32, 4.0f32);
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 5 previous errors
+error: use of a disallowed method `regex::Regex::new`
+  --> $DIR/conf_disallowed_methods.rs:18:61
+   |
+LL |     let indirect: fn(&str) -> Result<Regex, regex::Error> = Regex::new;
+   |                                                             ^^^^^^^^^^
+
+error: use of a disallowed method `f32::clamp`
+  --> $DIR/conf_disallowed_methods.rs:21:28
+   |
+LL |     let in_call = Box::new(f32::clamp);
+   |                            ^^^^^^^^^^
+
+error: use of a disallowed method `regex::Regex::new`
+  --> $DIR/conf_disallowed_methods.rs:22:53
+   |
+LL |     let in_method_call = ["^", "$"].into_iter().map(Regex::new);
+   |                                                     ^^^^^^^^^^
+
+error: aborting due to 8 previous errors